Abstract
Gaseous impurities, such as O2, are expected to be present within CO2 captured for storage. This could stimulate microbial activity in a geological CO2 storage site which has the potential to lead to operational issues such as injection well blockages, corrosion and oil souring. A series of experiments were carried out to examine the effect of 10 ppm and 100 ppm O2 in an anoxic (CO2 or N2) atmosphere on microbial communities and microbial gas production in laboratory scale experiments. Experiments inoculated with sulphate reducing bacteria enrichments were compared to uninoculated controls. The results show that H2S production is delayed in a CO2 atmosphere compared to the N2 atmosphere. 100 ppm O2 in CO2 resulted in a spike of H2S production as well as greater bacterial biomass when compared to the 10 ppm O2 in CO2 atmosphere. The inoculated N2 experiments showed similar patterns in H2S production and biomass regardless of O2 concentration. These results suggest that a concentration of O2 lower than 100 ppm in CO2 could reduce the potential for microbial growth and H2S production in CO2 storage sites. CH4 production was observed in some microcosms subsequent to H2S production, highlighting the potential for microbial methanogenesis in the in CCS reservoirs.
Highlights
The capture and storage of CO2 (CCS) in geological formations, such as deep saline aquifers, has the potential to reduce greenhouse gas emissions, which is needed to meet national and international targets (Committee on Climate Change, 2019; Parliament of the United Kingdom, 2008; UNFCCC Conference of the Parties, 1998)
Thia is of particular concern as sulphate reducing bacteria (SRB) in subsurface engineered environments have been connected to issues such as blockage of injection wells (Pellizzari et al, 2016; Zettlitzer et al, 2010), corrosion of the injection well pump in geothermal energy (Lerm et al, 2013), oil souring (Jordan and Walsh, 2004) and oil degradation during enhanced oil recovery (Jobson et al, 1979; Sherry et al, 2013)
Bacterial 16S rRNA and dsrB genes were detected in the uninoculated control experiments in a N2 at mosphere
Summary
The capture and storage of CO2 (CCS) in geological formations, such as deep saline aquifers, has the potential to reduce greenhouse gas emissions, which is needed to meet national and international targets (Committee on Climate Change, 2019; Parliament of the United Kingdom, 2008; UNFCCC Conference of the Parties, 1998). O2 is expected to be one of those impurities when CO2 is captured after the combustion of fuels for energy generation and it is estimated that its concentration could be as high as 6% depending on the combustion and capture technology used (Porter et al, 2015). Low concentrations of O2 have been shown to increase microbial breakdown of complex carbon sources and encourage the growth of anaerobic microbes (Chayabutra and Ju, 2000; Jordan and Walsh, 2004). Spore forming bacteria, in particular, have shown resilience to supercritical CO2 (Peet et al, 2015). It is recognised that both archaeal and bacterial groups are capable of (http://creativecommons.org/licenses/by/4.0/)
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